From that article:
"Human nature? It's the bananas, stupid.
During Jane Goodall's first four years studying chimpanzees in Tanzania, according to Sex at Dawn, she observed them to be remarkably peaceful creatures. But they were difficult to observe, since they tended not to hang around her camp much. So she tried to attract them nearer by regularly feeding them bananas. The effect, evidently, was to make the chimpanzees more aggressive. Fighting between them increased dramatically.
Now, which represented the chimpanzee's true nature? The gentle chimpanzees happily feeding far apart in the forest, not bothering each other? Or the hoodlum chimpanzees shoving each other out of the way at the daily banana trough?
The answer, as Ryan and Jetha eloquently express, is neither. It's like asking whether water's true nature is ice or liquid. It all depends on the conditions. Change the conditions, and you change which of many potential natures will be manifest."
This is such a true thing, and an excellent conceptual structure for understanding the practice of Buddha Dharma. In Buddha Dharma, we become what we practice at being. If we practice at being unkind, we become unkind. If we practice kindness, we become kind.... Our practice is part of the set of "conditions" which make up what we are and what we may become.